As is known in the art, many microelectronic circuits, particularly circuits that include amplifiers, as shown in FIG. 1A, sometimes during the design and fabrication process the installation of an attenuator, such as a broadband T-shaped attenuator as shown in FIGS. 1C-1E is sometimes required at some point along the signal path (sometimes referred to as the strip conductor or signal line, FIG. 1A) of a microstrip microwave transmission line. More particularly, the microstrip microwave transmission line includes the signal line separated from a circuit ground plane conductor by a substrate, as shown in FIG. 1A, and is used to interconnect a pair of amplifiers. It should be understood that if the microwave transmission line were a coplanar waveguide (CPW) microwave transmission line having the signal line disposed on the upper surface of a substrate and disposed between, and coplanar with, a pair of ground plane conductors, at least one of the coplanar ground plane conductors would be connected to the circuit ground plane with a conductive via passing through the substrate between the coplanar ground plane conductor of the CPW and the circuit ground plane conductor on the bottom surface of the substrate.
The attenuator has a pair of series resistive elements, disposed on an upper surface of a substrate, serially connected between an input pad and an output pad, and a shunt resistive element, also disposed on the upper surface of the substrate, connected between a junction between the pair of serially connected resistive elements and a shunt element pad. The shunt element pad is connected to an attenuator ground plane conductor disposed on the bottom surface of the attenuator substrate through a conductive via, as shown in FIGS. 1C-1E. The shunt element pad must be connected to the circuit ground plane conductor (which also serves as a DC ground connection) shown in FIG. 1B and therefore, the shunt elements pad, being connected to DC ground, must not be connected to the downstream amplifier input. Thus, as shown in FIG. 1B, when mounting the T-shaped attenuator to the signal line, FIG. 1B in order to prevent the shunt resistive element from being connected to the input of the downstream amplifier and also to enable the shunt element pad to be connected to the circuit ground plane conductor, a gap is formed in the signal line where an attenuator is to be installed, as shown in FIG. 1B. Thus, a via is formed through the substrate in a region between the signal line under the attenuator to the underlying circuit ground plane conductor, as shown in FIG. 1B. It would be describable to optimize the optimal point along the signal line for installation of the attenuator. Thus, using this gap approach the signal line has been permanently changed and thereby making installation of the attenuator at a different position along the signal line difficult. To put it another way, after creation of the gap and installation of the attenuator, testing may determine that the attenuator has not been installed at the optimum position. This gap approach has, however, permanently changed the signal line thereby making difficult to go back and change the position of the gap along the signal line where the attenuator is to be re-installed in order to obtain optimal performance. This results in costly amplifier rework and often means the replaced amplifiers have to be handpicked to make sure the signal level is corrected. This can make a major impact on a production line.